Land-water linkages and the biogeochemistry and ecology of Arctic aquatic ecosystems

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Rivers and lakes are powerful integrators of the landscapes that surround them. Changes on land are inevitably captured by water flowing across landscapes, which is ultimately delivered to aquatic environments. Thus, aquatic ecosystems both capture, and are affected by, change occurring across broad spatial scales. This is particularly important in the north because permafrost - the permanently frozen ground that covers about half of Canada's landmass - is thawing throughout the Arctic. Thus, constituents currently 'locked away' (sequestered) in permafrost are becoming available for reaction within and liberation from soils, and transport to aquatic environments. Working at sites experiencing massive permafrost slumping in the western Canadian Arctic, this research will examine how permafrost thaw changes the land-to-water flux of dissolved inorganic and organic carbon (DIC, DOC), and the implications of this change for the larger carbon (C) cycle. Bicarbonate, which is typically the main component of the aquatic DIC pool, is largely produced by chemical weathering, whereby CO2 dissolved in water reacts with the mineral component of soils, causing the original CO2 to become 'fixed' as bicarbonate. Alongside photosynthesis, weathering is one of two main sequestration mechanisms for CO2 on land. In contrast, permafrost soils contain about twice as much organic C as currently exists in the atmosphere as CO2, and thus DOC mobilized from thawing permafrost represents a future CO2 source, following its degradation by bacteria or sunlight. Although research exploring the C dynamics of permafrost thaw has focused almost exclusively on organic C degradation, our early work has shown that increased weathering in newly-thawed mineral soils may temper the effect of CO2 release from organic C as permafrost thaws. This research will undertake a unique, concurrent investigation of the counterbalancing effects of permafrost thaw on inorganic and organic C cycling in the western Canadian Arctic, and train multiple southern personnel and northern residents. Because of the many constituents released as permafrost thaws, this work will also bolster understanding of the socio-economic and environmental effects of permafrost thaw on northern freshwaters.